Semiconductor devices having different gate oxide thicknesses

ABSTRACT

A method of manufacturing multiple finFET devices having different thickness gate oxides. The method may include depositing a first dielectric layer on top of the semiconductor substrate, on top of a first fin, and on top of a second fin; forming a first dummy gate stack; forming a second dummy gate stack; removing the first and second dummy gates selective to the first and second gate oxides; masking a portion of the semiconductor structure comprising the second fin, and removing the first gate oxide from atop the first fin; and depositing a second dielectric layer within the first opening, and within the second opening, the second dielectric layer being located on top of the first fin and adjacent to the exposed sidewalls of the first pair of dielectric spacers, and on top of the second gate oxide and adjacent to the exposed sidewalls of the second pair of dielectric spacers.

CROSS REFERENCE

The present application is a divisional of and claims priority under 35U.S.C. §120 of U.S. patent application Ser. No. 13/534,012, filed onJun. 27, 2012, which is incorporated by reference in its entirety.

BACKGROUND

The present disclosure generally relates to integrated circuits, andmore particularly to fabricating semiconductor devices having differentthickness gate oxides on the same semiconductor substrate.

An increasing demand exists for providing semiconductor devices havinggate oxide layers of varying thicknesses, for example field effecttransistors (FET). In fact, the gate oxide thickness is a major concernin terms of reliability when providing integrated circuit devicescontaining transistors and other circuit elements that operate atdiffering voltage levels. By way of example, a relatively thin gateoxide may typically range from 8 Å to 20 Å in thickness, while arelatively thick gate oxide may typically range from 12 Å to 60 Å inthickness.

Device scaling trends have led to low voltage operation with relativelythin gate oxide; whereas, some circuit applications still require arelatively thick gate oxide, such as driver or receiver circuitry at thechip I/O, and some analog output devices. The thick gate oxide isnecessary for high voltage devices in order to ensure reliability, whilethe thin gate oxide is desirable for the relatively fast logic devicesthat use low voltages at the gate. Use of relatively thick gate oxidefor the lower voltage transistors cause poor device performance andsignificantly decrease the speed, therefore the need for multiplethickness gate oxides.

Moreover, with the trend of trying to put as many different circuits aspossible in the same chip to achieve more functionality and improvedperformance (such as Merged logic-DRAM, embedded NVM micro-controls),there are even more different possible combinations for different partsof circuits in the same chip to have different gate oxide thickness toachieve the optimized performance and reliability at the system level.

Referring to FIG. 22, typical fabrication of a semiconductor device,such as a planar FET, includes oxidizing a surface of a substrate 202 toform a dielectric layer. The oxidized dielectric layer may be referredto as a grown dielectric layer. Next, a layer of polysilicon may bedeposited on top of the grown dielectric layer. The grown dielectriclayer and the polysilicon layer are patterned and etched to form dummygate stacks. Each dummy gate stack has a gate oxide made from the growndielectric layer. The gate oxides may a common thickness. Also, eachgate stack includes a dummy gate (not shown) made from the polysiliconlayer.

After etching the gate stacks spacers 210 a, 210 b, 216 a, 216 b may beformed on opposite sides of each dummy gate stack as shown in thefigure. Next, an inter layer dielectric (ILD) material 204 may bedisposed between the devices to electrically insulate one device fromanother. The ILD material 204 may be polished preferably using achemical and mechanical polishing (CMP) process to expose the tops ofthe dummy gates stacks. The exposed polysilicon dummy gates (note shown)may then be removed using an etching process and are typically replacedwith a metal gate terminal 208, 214. The dummy gates may be replacedwith a metal or any other semiconducting material known to a person ofordinary skill in the art. Alternatively, the entire dummy gate stackincluding the polysilicon dummy gate and the gate oxide may be removedwith an etching technique and replaced with a high-k dielectric andmetal gate terminal. This technique may be referred to as replacementgate (RG) or gate-last processing.

During the RG processing there exists a potential for the thickness ofthe gate oxide to be compromised by the etching process during theremoval of the polysilicon dummy gate in preparation for depositing agate terminal 208, 214. The thickness of the gate oxide may be harmed byeither the etchants used to remove the polysilicon dummy gates or a postetching process, typically RIE, used to clean and remove polymersattacking the underlying gate oxide 206.

Further, to fabricate different gate oxide thicknesses (e.g. 206 and212) on the same semiconductor substrate an additional iteration of theprocess described above (oxidize-mask-etch) is required for eachadditional thickness desired. However, such an approach typicallysignificantly increases the overall manufacturing cost and degrades thereliability as well as yield due to the potential contamination causedby resist residues from the patterning required. Besides, controllingthe gate oxide thickness is more difficult because the thick oxide layerresults from the combination of multiple oxide formation cycles, and itmay be damaged by the etching process described above. This introducesmultiple sources of variability due to the multiple steps required tofabricate the thick gate oxide layers. Additionally, theoxidize-mask-etch process described above may cause ILD loss because theILD remains unprotected during processing. An unprotected ILD can haverecesses that fill with Al or other metals during replacement gateprocessing. Excess metal collected in these recesses can lead to a shortcircuit.

A similar RG technique may be used to fabricate finFET devices.Fabrication of finFET devices using RG techniques includes patterningand etching fins into a semiconductor substrate. The semiconductorsubstrate may include any bulk substrate or SOI substrate know to aperson of ordinary skill in the art. A first gate dielectric may begrown on the fins by oxidizing the surface of the semiconductorsubstrate. The process of growing the first gate dielectric includesoxidizing the surface of the semiconductor substrate. This processconsumes some of the semiconductor material in effect reducing the widthof the fins. Next, a polysilicon layer may be deposited on top of thegate dielectric layer from which dummy gates may be pattered and etched.After etching, a portion of the gate dielectric may remain beneath thedummy gates, and the dummy gate and gate dielectric form dummy gatestacks. A pair of spacers may be disposed on opposite sidewalls of eachdummy gate stacks. The dummy gates may then be removed to createopenings. Some openings may be masked while others may remain open. Asecond gate dielectric may be grown on top of the first gate dielectricin the unmasked openings. Next, the mask may be removed and metal gateterminals may be formed in the openings between the spacers and on topof the first gate dielectric and the second gate dielectric.

SUMMARY

According to one embodiment of the present disclosure, a method ofmanufacturing a semiconductor structure including multiple finFETdevices each including different thickness gate oxides and formed in asemiconductor substrate is provided. The method may include depositing afirst dielectric layer on top of the semiconductor substrate, on top ofa first fin, and on top of a second fin, forming a first dummy gatestack including a first dummy gate located on top of a first gate oxideabove the first fin, and a first pair of dielectric spacers disposed onopposite sides of the first dummy gate stack, and forming a second dummygate stack including a second dummy gate located on top of a second gateoxide above the second fin, and a second pair of dielectric spacersdisposed on opposite sides of the second dummy gate stack. The methodmay also include removing the first dummy gate and the second dummy gateselective to the first and second gate oxides, and creating a firstopening defined by exposed sidewalls of the first pair of dielectricspacers and a second opening defined by exposed sidewalls of the secondpair of dielectric spacers, masking a portion of the semiconductorstructure including the second fin, and removing the first gate oxidefrom atop the first fin, and depositing a second dielectric layer withinthe first opening, and within the second opening, the second dielectriclayer being located on top of the first fin and adjacent to the exposedsidewalls of the first pair of dielectric spacers, the second dielectriclayer being located on top of the second gate oxide and adjacent to theexposed sidewalls of the second pair of dielectric spacers.

According another exemplary embodiment, a semiconductor structureincluding multiple finFET devices each including different thicknessgate oxides and formed in a semiconductor substrate is provided. Thestructure may include a semiconductor substrate including a first finand a second fin, a first gate stack including a first terminal locatedabove the first fin, and a first pair of dielectric spacers disposed onopposite sides of the first gate stack, the first gate stack including adielectric layer located between the first fin and the gate terminal andbetween the gate terminal and the pair of spacers, and a second gatestack including a gate oxide and a second terminal located above thesecond fin, and a second pair of dielectric spacers disposed on oppositesides of the second gate stack, the gate oxide being located on top ofthe second fin and the gate terminal being located on top of the gateoxide, the second gate stack including the dielectric layer locatedbetween the gate oxide and the gate terminal and between the gateterminal and the pair of spacers.

BRIEF DESCRIPTION FO THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description, given by way of example and notintend to limit the disclosure solely thereto, will best be appreciatedin conjunction with the accompanying drawings, in which:

FIGS. 1-21 illustrate the steps of a method of fabricating asemiconductor structure according to one embodiment.

FIG. 1 depicts an isometric view of a first and a second fin formed in asemiconductor substrate according to one embodiment.

FIG. 2 depicts the deposition of a first dielectric layer according toone embodiment.

FIG. 3 depicts the deposition of a sacrificial layer according to oneembodiment.

FIG. 4 depicts the formation of dummy gates according to one embodiment.

FIG. 5 depicts the formation of spacers on opposite sides of the dummygates according to one embodiment.

FIG. 6 depicts the deposition of an inter-layer dielectric formed on topof the semiconductor substrate and surrounding the dummy gates accordingto one embodiment.

FIG. 7 depicts the removal of the dummy gates according to oneembodiment.

FIG. 8 depicts cross-sectional view A-A of FIG. 7, in which the dummygates are removed.

FIG. 9 depicts cross-sectional view B-B of FIG. 7, in which the dummygates are removed.

FIG. 10 depicts the deposition of a resist mask on top of the firstdielectric layer above the second fin and the subsequent removal of thefirst dielectric layer from atop the first fin according to oneembodiment.

FIG. 11 depicts cross-sectional view C-C of FIG. 10, in which the firstdielectric layer is removed from atop the first fin.

FIG. 12 depicts cross-sectional view D-D of FIG. 10, in which the firstdielectric layer is removed from atop the first fin.

FIG. 13 depicts cross-sectional view E-E of FIG. 10, in which the firstdielectric layer is removed from atop the first fin.

FIG. 14 depicts the deposition of a second dielectric layer on top ofthe first fin and on top of the first dielectric layer above the secondfin according to one embodiment.

FIG. 15 depicts cross-sectional view F-F of FIG. 14, in which the seconddielectric layer is deposited on top of the first fin and on top of thefirst dielectric layer above the second fin.

FIG. 16 depicts cross-sectional view F-F of FIG. 14, in which the seconddielectric layer is deposited on top of the first fin and on top of thefirst dielectric layer above the second fin.

FIG. 17 depicts cross-sectional view F-F of FIG. 14, in which the seconddielectric layer is deposited on top of the first fin and on top of thefirst dielectric layer above the second fin.

FIG. 18 depicts the deposition of gate terminals on top of the seconddielectric layer according to one embodiment.

FIG. 19 depicts cross-sectional view I-I of FIG. 18, in which gateterminals are formed on top of the second dielectric layer.

FIG. 20 depicts cross-sectional view I-I of FIG. 18, in which gateterminals are formed on top of the second dielectric layer.

FIG. 21 depicts cross-sectional view I-I of FIG. 18, in which gateterminals are formed on top of the second dielectric layer.

FIG. 22 is a cross-sectional side view diagram of a conventionalsemiconductor structure with two planar FET devices each havingdifferent thickness gate oxides.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it can be understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. This disclosure may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiment set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the scope of this disclosure to thoseskilled in the art. In the description, details of well-known featuresand techniques may be omitted to avoid unnecessarily obscuring thepresented embodiments.

The drawings are not necessarily to scale. The drawings are merelyschematic representations, not intended to portray specific parametersof the invention. The drawings are intended to depict only typicalembodiments of the invention. In the drawings, like numbering representslike elements.

A finFET device includes a plurality of fins formed in a wafer; a gatecovering a portion of the fins, wherein the portion of the fins coveredby the gate serves as a channel region of the device and portions of thefins extending out from under the gate serve as source and drain regionsof the device; and spacers on opposite sides of the gate.

In a RG fabrication approach, a semiconductor substrate may be patternedand etched to form fins. Next, a dummy gate may be formed in a directionperpendicular to the length of the fins. For example, the dummy gate maybe pattered and etched from a polysilicon layer. A pair of spacers canbe disposed on opposite sidewalls of the dummy gate. Later, the dummygate may be removed from between the pair of spacers, as by, forexample, an anisotropic vertical etch process such as a reactive ionetch (RIE). This creates an opening between the spacers where a metalgate may then be formed between the spacers. A gate dielectric may beconfigured below the metal gate. Devices may include gate dielectricswith different thicknesses. Formation of multiple finFET devices havingdifferent thickness gate dielectrics using RG fabrication techniques isdescribed in greater detail below.

Referring now to FIGS. 1-15, exemplary process steps of forming FETs,such as finFETs, having different thickness gate oxides on a singlesemiconductor integrated circuit in accordance with one embodiment ofthe present invention are shown. In particular, a high performancefinFET device may have a thin gate oxide, and an I/O finFET device mayhave a thick gate oxide. Standard replacement gate (RG) processingtechniques, as described above, may be used to form both highperformance finFET devices and I/O finFET devices. The particularprocess point in which the gate oxide layers are formed during standardRG processing may vary. These variations are described in detail belowas different embodiments.

Referring now to FIG. 1, a first fin 102 and a second fin 104 are shownformed in an SOI substrate. It should be noted that the fins 102 and 104may be formed in any semiconductor substrate know to a person havingordinary skill in the art. The first fin 102 depicts the beginningstages of the fabrication of a single high performance device while thesecond fin 104 depicts the beginning stages of the fabrication of asingle I/O device. It should be noted that a single integrated circuitmay include multiple high performance devices and multiple I/O devices.Conventional photolithography techniques known to a person havingordinary skill in the art may be used to form the fins 102, 104 in theSOI substrate.

With continued reference to FIG. 1, a silicon-on-insulator (SOI)substrate 140 is shown. The SOI substrate 140 may include a buried oxide(BOX) layer 142 and a silicon-on-insulator (SOI) layer 144 formed on topof the BOX layer 142. In one embodiment, the SOI substrate 140 may havean oxide layer 146 and a nitride layer 148 formed on a top surface ofthe SOI layer 144, where the nitride layer 148 may be located directlyon top of the oxide layer 146.

The BOX layer 142 may be formed from any of several dielectricmaterials. Non-limiting examples include, for example, oxides, nitridesand oxynitrides of silicon. The BOX layer 142 may also include oxides,nitrides and oxynitrides of elements other than silicon. In addition,the BOX layer 142 may include crystalline or non-crystalline dielectricmaterial. Moreover, the BOX layer 142 may be formed using any of severalmethods. Non-limiting examples include ion implantation methods, thermalor plasma oxidation or nitridation methods, chemical vapor depositionmethods and physical vapor deposition methods. The BOX layer 142 mayinclude a thickness ranging from about 5 nm to about 200 nm. In oneembodiment, the BOX layer 142 may be about 25 nm thick.

The SOI layer 144 may be made from any of several known semiconductormaterials such as, for example, a bulk silicon substrate. Othernon-limiting examples include silicon, germanium, silicon-germaniumalloy, silicon carbide, silicon-germanium carbide alloy, and compound(e.g. III-V and II-VI) semiconductor materials. Non-limiting examples ofcompound semiconductor materials include gallium arsenide, indiumarsenide, and indium phosphide. Typically, the SOI layer 144 includes athickness ranging from about 5 nm to about 100 nm. Methods for makingthe SOI layer 144 are well known in the art. Non-limiting examplesinclude SIMOX (Separation by Implantation of OXygen), wafer bonding, andELTRAN® (Epitaxial Layer TRANsfer).

The oxide layer 146 may include a silicon oxide or a silicon oxynitride.In one embodiment, the oxide layer 146 can be formed, for example, bythermal or plasma conversion of a top surface of the SOI layer 144 intoa dielectric material such as silicon oxide or silicon oxynitride. Inone embodiment, the oxide layer 146 can be formed by deposition ofsilicon oxide or silicon oxynitride by chemical vapor deposition (CVD)or atomic layer deposition (ALD). The oxide layer 146 may have athickness ranging from about 1 nm to about 10 nm, although a thicknessless than 1 nm and greater than 10 nm may be acceptable. In oneembodiment, the oxide layer 146 may be about 5 nm thick.

The nitride layer 148 may include an insulating material such as, forexample, silicon nitride. The nitride layer 148 may be formed usingconventional deposition methods, for example, low-pressure chemicalvapor deposition (LPCVD). In one embodiment, the nitride layer 148 mayhave a thickness ranging from about 5 nm to about 100 nm. In oneparticular embodiment, the nitride layer 148 may be about 50 nm thick.

Referring now to FIG. 2, a first dielectric layer 106 may be depositedconformal to the surface of the SOI substrate 140, the first fin 102,and the second fin 104. In one embodiment, the first dielectric layer106 may include, but is not limited to, a material made from hafniumsilicate (HfSiO_(x)), hafnium oxide (HfO2), zirconium silicate(ZrSiO_(x)), zirconium oxide (ZrO₂), silicon nitride (Si₃N₄), siliconoxynitride (SiON), or other high-k material (greater than 4.0) or anycombination of these materials. In one embodiment, the first dielectriclayer 106 may include silicon oxide (SiO₂) deposited using an atomiclayer deposition (ALD) technique. The first dielectric layer 106 mayhave a thickness ranging from about 12 Å to 60 Å, although a thicknessof the first dielectric layer 106 less than 12 Å or greater than 60 Å isacceptable.

Now referring to FIG. 3, a sacrificial layer 107 is formed on top of thefirst dielectric layer 106. The sacrificial layer 107 may be used toform dummy gates to be used in conjunction with standard replacementgate processing. The sacrificial layer 107 may be deposited using anysuitable technique such as atomic layer deposition (ALD), chemical vapordeposition (CVD), or physical vapor deposition (PVD). In one embodiment,the sacrificial layer 107 may be made from polysilicon. A chemicalmechanical polishing (CMP) technique may be used to smooth a top surfaceof the sacrificial layer 107.

With continued reference to FIG. 3, a first resist mask 108 may beapplied to the top surface of the sacrificial layer 107. Conventionalphotolithography techniques known to a person having ordinary skill inthe art may be used to pattern dummy gates (shown in FIG. 4) from thesacrificial layer 107 using the first resist mask 108. Portions of thesacrificial layer 107 and the first dielectric layer 106 not covered bythe first resist mask 108 may be removed selective to the BOX layer 142,the first fin 102, and the second fin 104. In one embodiment, forexample, reactive ion etching (RIE) may be used to remove thesacrificial layer 107 and the first dielectric layer 106 not covered bythe resist mask.

Now referring to FIG. 4, a first gate stack 109 and a second gate stack111 patterned from the sacrificial layer 107, FIG. 3, and the firstdielectric layer 106 are shown. The first resist mask 108, FIG. 3, maybe removed after patterning of the first and second gate stacks 109 and111. The first gate stack 109 may include a first dummy gate 110 and aportion of the first dielectric layer 106. The second gate stack 111 mayinclude a second dummy gate 112 and a portion of the first dielectriclayer 106.

Now referring to FIG. 5, a first pair of dielectric spacers 114 a, 114 bmay be formed on opposite sides of the first dummy gate 110 and a secondpair of dielectric spacers 116 a, 116 b may be formed on opposite sidesof the second dummy gate 112. Conventional photolithography techniquesknown to a person having ordinary skill in the art may be used to formthe first pair of dielectric spacers 114 a, 114 b and the second pair ofdielectric spacers 116 a, 116 b.

Now referring to FIG. 6, an interlayer dielectric (ILD) material 118,deposited on top of the SOI substrate 140, the first fin 102, the secondfin 104, the first pair of spacers 114 a, 114 b, and the second pair ofspacers 116 a, 116 b, is shown. A CMP technique may be used to smooth atop surface of the ILD material 118, the first dummy gate 110, and thesecond dummy gate 112.

Now referring to FIG. 7, the first dummy gate 110, FIG. 6, and thesecond dummy gate 112, FIG. 6, may be removed selective to the firstdielectric layer 106. In one embodiment, isotropic wet etching may beused to remove the first dummy gate 110, FIG. 6, and the second dummygate 112, FIG. 6. In one embodiment, the isotropic wet etching techniquemay use one of the following compounds, tetra methyl ammonium hydroxide(TMAH), warm or hot ammonia, or hot tetra eethyl ammonium hydroxide(TEMH). In on embodiment, the isotropic wet etching technique may useammonium hydroxide. In one embodiment, for example, reactive ion etching(RIE) may be used to remove the first dummy gate 110, FIG. 6, and thesecond dummy gate 112, FIG. 6. Removal of the first dummy gate 110, FIG.6, and the second dummy gate 112, FIG. 6, creates a first opening 120and a second opening 122, as shown in the figure.

FIGS. 8 and 9 each depict a cross-sectional view of FIG. 7. Crosssection A-A is depicted in FIG. 8. Cross section B-B is depicted in FIG.9. Referring to both FIGS. 8 and 9, the first dielectric layer 106 isshown conformal to the BOX layer 142, the first fin 102, and the secondfin 104, but only in the openings 120, 122, FIG. 7, created by theremoval of the first dummy gate 110, FIG. 6, and the second dummy gate112, FIG. 6. Therefore, the first dielectric layer 106 may be depositedconformal to the fins 102, 104 of both the high performance finFETdevice and the I/O finFET device, as shown in the figure.

Referring now to FIG. 10, a second resist mask 124 is shown in place ofthe second dummy gate 112, FIG. 6, in the second opening 122, FIG. 7.After the second dummy gate 112, FIG. 6, is removed the second resistmask 124 may be applied directly on top of the first dielectric layer106, but only within the second opening 122, FIG. 7. The second resistmask 124 may be not applied on top of the first dielectric layer 106within the first opening 120.

Therefore, the second resist mask 124 may be applied directly on top ofthe first dielectric later 106 of the I/O finFET device and not on topof the first dielectric layer 106 of the high performance finFET device.The first dielectric layer 106 may then be removed from all areas notprotected by the second resist mask 124. More specifically, an etchingtechnique may be used to remove the first dielectric layer 106 fromwithin the first opening 120 selective to the BOX layer 142 and the fin102. In one embodiment, isotropic wet etching may be used to remove thefirst dielectric layer 106. In one embodiment, the isotropic wet etchingtechnique may use one of the following compounds, tetra methyl ammoniumhydroxide (TMAH), warm or hot ammonia, or hot tetra eethyl ammoniumhydroxide (TEMH). In one embodiment, the isotropic wet etching techniquemay use ammonium hydroxide. In one embodiment, for example, reactive ionetching (RIE) may be used to remove the first dielectric layer 106 fromwithin the first opening 120. Therefore, the removal technique describedabove removes the first dielectric layer 106 only from within the firstopening 120 and not from within the second opening 122, FIG. 7.Therefore, the first dielectric layer 106 remains within the secondopening 122, FIG. 7 and on top of the second fin 104 of the I/O deviceafter the removal process described above.

Removal of the first dielectric layer 106 from within the first opening120 exposes the BOX layer 142 and first fin 102 within that opening. Thesurface of the BOX layer 142 and the first fin 102 remain undamagedthroughout the removal process because the etching technique may belimited to remove on the deposited thickness of the first dielectriclayer 106. This is possible because the first dielectric layer 106 maybe deposited conformal to the surface geometry of the BOX layer 142 andthe first fin 102 and have a constant thickness.

FIGS. 11, 12, and 13 each depict a cross-sectional view of FIG. 10.Cross section C-C is depicted in FIG. 11. Cross section D-D is depictedin FIG. 12. Cross section E-E is depicted in FIG. 13. Referring to FIGS.11, 12 and 13, the first dielectric layer 106 is shown conformal to theBOX layer 142 and the second fin 104 within the second opening 122, FIG.7. The first dielectric layer 106 is no longer shown conformal to theBOX layer 142 and the first fin 102 within the first opening 120.Therefore the first dielectric layer 106 remains deposited conformal tothe second fin 104 of the I/O finFET device and no longer exists on topof the first fin 102 of the high performance device.

Referring now to FIG. 14, a second dielectric layer 126 may be depositedconformal to the surface of the SOI substrate 140 and the first fin 102within the first opening 120, and conformal to the first dielectriclayer 106 within the second opening 122. In one embodiment, the seconddielectric layer 126 may include, but is not limited to, a material madefrom hafnium silicate (HfSiO_(x)), hafnium oxide (HfO₂), zirconiumsilicate (ZrSiO_(x)), zirconium oxide (ZrO₂), silicon nitride (Si₃N₄),silicon oxynitride (SiON), or other high-k material (greater than 4.0)or any combination of these materials. In one embodiment, the seconddielectric layer 126 may include silicon oxide (SiO₂) deposited using anatomic layer deposition (ALD) technique. The second dielectric layer 126may have a thickness ranging from about 8 Å to 20 Å, although athickness of the second dielectric layer 126 less than 8 Å or greaterthan 20 Å is acceptable.

FIGS. 15, 16, and 17 each depict a cross-sectional view of FIG. 14.Cross section F-F is depicted in FIG. 15. Cross section G-G is depictedin FIG. 16. Cross section H-H is depicted in FIG. 17. Referring to FIGS.15, 16 and 17, the second dielectric layer 126 is shown conformal to theSOI substrate 140 and the first fin 102 within the first opening 120,and conformal to the first dielectric layer 106 within the secondopening 122. Therefore, the second dielectric layer 126 may serve as thegate oxide for the high performance device and both the first dielectriclayer 106 and the second dielectric layer 126 may serve as the gateoxide for the 110 device.

Referring now to FIG. 18, a first gate terminal 128 and a second gateterminal 130 may be deposited. The formation of the gate terminals 128,130 may include any now known or later developed replacement gatetechniques. The first gate terminal 128 and the second gate terminal 130may include any work function metal, seal metal, or low resistance bulkmetal fill appropriate for the finFET device to be created. For example,materials such as aluminum, titanium nitride (TiN) ruthenium (Ru),titanium aluminum (TiAl), tantalum nitride (TaN), or tantalum carbide(TaC) may be used. Although shown as a single metal deposition, it isunderstood that multiple metal depositions using appropriate maskingtechniques may be employed to provide the appropriate metal over thecorrect areas. In one embodiment, a high-k layer may be deposited on topof the gate oxides before depositing the gate terminals. Finally, a CMPprocess may be used to remove excess metal deposited on the top surfaceof the ILD material 118 during the formation of the first gate terminal128 and the second gate terminal 130.

FIGS. 19, 20, and 21 each depict a cross-sectional view of FIG. 18.Cross section I-I is depicted in FIG. 19. Cross section J-J is depictedin FIG. 20. Cross section K-K is depicted in FIG. 21. Referring to FIGS.19, 20 and 21, the first gate terminal 128 is shown on top of the seconddielectric layer 126 above the first fin 102, and the second gateterminal 130 is shown on top of the second dielectric layer 126 abovethe first dielectric layer 106 and the second fin 104. Therefore, thefirst gate terminal 128 may serve as the gate terminal for the highperformance device and the second gate terminal 130 may serve as thegate terminal for the I/O device.

Without reference to a particular drawing or set of drawings onevariation of the above process is described below. In one embodiment,the sacrificial layer 107 may be deposited on top of the first andsecond fins 102, 104 followed by a CMP technique to smooth the topsurface of the sacrificial layer 107. Next, the first dummy gate 110 andthe second dummy gate 112 may be formed from the sacrificial layer 107using conventional photolithography techniques. The spacers 114 a, 114b, 116 a, 116 b may then be formed on opposite sides of the dummy gates110, 112. Next, the ILD material 118 may be deposited on top of the SOIsubstrate, the first fin 102, the second fin 104, the first pair ofspacers 114 a, 114 b, and the second pair of spacers 116 a, 116 b. A CMPtechnique may be used to smooth the top surface of the ILD material 118,the first dummy gate 110, and the second dummy gate 112. The dummy gates110, 112 may then be removed selective to the second dielectric layer126 crating the openings 120, 122.

Next, a resist mask (not shown) may be applied above the first fin 102and the first dielectric layer 106 may be deposited conformal to thesurface of the SOI substrate and the second fin 104, but only within theopening 122. The resist mark may then be removed and another resist mask(not shown) may be deposited directly on top of the first dielectric 106layer formed over the second fin 104. Next, the second dielectric layer126 may be deposited conformal to the surface of the SOI substrate andthe first fin 102, but only within the opening 120. After the anotherresist mask is removed, gate terminals 128, 130 may then be formedwithin the openings 120, 122, and on top of the first dielectric layer106 and the second dielectric layer 126.

Without reference to a particular drawing or set of drawings onevariation of the above process is described below. In one embodiment,the first dielectric layer 106 may be deposited conformal to the surfaceof the SOI substrate, the first fin 102, and the second fin 104. Next, asecond resist mask 124 may be deposited directly on top of the firstdielectric 106 layer formed over the second fin 104. The second resistmask 124 may not be deposited on top of the first dielectric layer 106formed over the first fin 102. The first dielectric layer 106 may thenbe removed from atop the first fin 102. Next, the second dielectriclayer 126 may be deposited on top of the first fin 102 and on top of thefirst dielectric layer 106. The sacrificial layer 107 may then bedeposited on top of the second dielectric layer 126 followed by a CMPtechnique to smooth the top surface of the sacrificial layer 107.

Next, the first dummy gate 110 and the second dummy gate 112 may beformed from the sacrificial layer 107 using conventionalphotolithography techniques. The spacers 114 a, 114 b, 116 a, 116 b maythen be formed on opposite sides of the dummy gates 110, 112. Next, theILD material 118 may be deposited on top of the SOI substrate, the firstfin 102, the second fin 104, the first pair of spacers 114 a, 114 b, andthe second pair of spacers 116 a, 116 b. A CMP technique may be used tosmooth the top surface of the ILD material 118, the first dummy gate110, and the second dummy gate 112. The dummy gates 110, 112 may then beremoved selective to the second dielectric layer 126 crating theopenings 120, 122. Next, gate terminals 128, 130 may be formed withinthe openings 120, 122.

Without reference to a particular drawing or set of drawings onevariation of the above process is described below. In one embodiment, athin barrier layer can be deposited on to the surface of the SOIsubstrate, the first fin 102, and the second fin 104. The thin barrierlayer may be made from a material that will allow for easy removal ofthe sacrificial layer without causing damage to the underlyingsubstrate. In one embodiment, the thin barrier layer may be made from anoxide or a nitride. Next, the sacrificial layer 107 may be deposited ontop of the thin barrier layer followed by a CMP technique to smooth thetop surface of the sacrificial layer 107. Next, the first dummy gate 110and the second dummy gate 112 may be formed from the sacrificial layer107 using conventional photolithography techniques. The spacers 114 a,114 b, 116 a, 116 b may then be formed on opposite sides of the dummygates 110, 112. Next, the ILD material 118 may be deposited on top ofthe SOI substrate, the first fin 102, the second fin 104, the first pairof spacers 114 a, 114 b, and the second pair of spacers 116 a, 116 b. ACMP technique may be used to smooth the top surface of the ILD material118, the first dummy gate 110, and the second dummy gate 112. The dummygates 110, 112 may then be removed selective to the thin barrier layercrating the openings 120, 122.

Next, the first dielectric layer 106 may be deposited conformal to thesurface of the SOI substrate, the first fin 102, and the second fin 104,but only within the openings 120, 122. A second resist mask 124 may bedeposited directly on top of the first dielectric 106 layer formed overthe second fin 104. The second resist mask 124 may not be deposited ontop of the first dielectric layer 106 formed over the first fin 102.Next, the first dielectric layer 106 may be removed from atop the firstfin 102. Next, the second dielectric layer 126 may be deposited on topof the first fin 102 and on top of the first dielectric layer 106. Gateterminals 128, 130 may then be formed within the openings 120, 122.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiment, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A semiconductor structure comprising multiplefinFET devices each comprising different thickness gate oxides andformed in a semiconductor substrate, the structure comprising: asemiconductor substrate comprising a first fin and a second fin; a firstgate stack comprising a first terminal located above the first fin, anda first pair of dielectric spacers disposed on opposite sides of thefirst gate stack, the first gate stack comprising a dielectric layerlocated between the first fin and the gate terminal and between the gateterminal and the pair of spacers; a second gate stack comprising a gateoxide and a second terminal located above the second fin, and a secondpair of dielectric spacers disposed on opposite sides of the second gatestack, the gate oxide being located on top of the second fin and thegate terminal being located on top of the gate oxide, the second gatestack comprising the dielectric layer located between the gate oxide andthe gate terminal and between the gate terminal and the pair of spacers.2. The structure of claim 1, wherein the gate oxide and the dielectriclayer comprises a high-k dielectric material.
 3. The structure of claim1, wherein the first and second gate terminals comprises polysilicon,aluminum, or tungsten.